WO2001029987A1 - AN ADAPTIVE DIGITAL BEAMFORMING RECEIVER WITH π/2 PHASE SHIFT TO IMPROVE SIGNAL RECEPTION - Google Patents
AN ADAPTIVE DIGITAL BEAMFORMING RECEIVER WITH π/2 PHASE SHIFT TO IMPROVE SIGNAL RECEPTION Download PDFInfo
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- WO2001029987A1 WO2001029987A1 PCT/EP2000/009761 EP0009761W WO0129987A1 WO 2001029987 A1 WO2001029987 A1 WO 2001029987A1 EP 0009761 W EP0009761 W EP 0009761W WO 0129987 A1 WO0129987 A1 WO 0129987A1
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- equalizer circuit
- feedforward equalizer
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
- H01Q3/2605—Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
- H01Q3/2611—Means for null steering; Adaptive interference nulling
- H01Q3/2617—Array of identical elements
- H01Q3/2623—Array of identical elements composed of two antennas
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/015—High-definition television systems
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
- H01Q3/2605—Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
- H01Q3/2611—Means for null steering; Adaptive interference nulling
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/30—Time-delay networks
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
- H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
- H04B7/0842—Weighted combining
- H04B7/0845—Weighted combining per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
- H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
- H04B7/0842—Weighted combining
- H04B7/086—Weighted combining using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03012—Arrangements for removing intersymbol interference operating in the time domain
- H04L25/03019—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception
- H04L25/03057—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception with a recursive structure
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q3/00—Selecting arrangements
- H04Q3/18—Circuit arrangements for first stage of hunting switching
- H04Q3/24—Circuit arrangements for first stage of hunting switching for line finders
- H04Q3/26—Circuit arrangements for first stage of hunting switching for line finders comprising common calling and disconnecting circuit
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/16—Circuits
- H04B1/26—Circuits for superheterodyne receivers
- H04B1/28—Circuits for superheterodyne receivers the receiver comprising at least one semiconductor device having three or more electrodes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/0335—Arrangements for removing intersymbol interference characterised by the type of transmission
- H04L2025/03375—Passband transmission
- H04L2025/03382—Single of vestigal sideband
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/03433—Arrangements for removing intersymbol interference characterised by equaliser structure
- H04L2025/03439—Fixed structures
- H04L2025/03445—Time domain
- H04L2025/03471—Tapped delay lines
- H04L2025/03484—Tapped delay lines time-recursive
- H04L2025/0349—Tapped delay lines time-recursive as a feedback filter
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/03592—Adaptation methods
- H04L2025/03598—Algorithms
- H04L2025/03611—Iterative algorithms
- H04L2025/03617—Time recursive algorithms
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/41—Structure of client; Structure of client peripherals
- H04N21/426—Internal components of the client ; Characteristics thereof
- H04N21/42607—Internal components of the client ; Characteristics thereof for processing the incoming bitstream
- H04N21/4263—Internal components of the client ; Characteristics thereof for processing the incoming bitstream involving specific tuning arrangements, e.g. two tuners
Definitions
- the present invention is directed, in general, to antenna systems and signal receivers and, more specifically, to an apparatus and method for improving the reception of signals such as digital television signals, e.g., ATSC 8-NSB signals.
- signals such as digital television signals, e.g., ATSC 8-NSB signals.
- Many digital television receivers have internal antennas or are connected to indoor antennas. In such digital television receivers there can be problems in receiving a good quality signal due to the presence of multiple signal echoes created by obstacles in the room.
- the multiple signal echoes are inteferer signals that arrive late at the antenna (i.e., multipath delay).
- the indoor antenna may be manually rotated or adjusted to maximize the main signal and minimize the unwanted signals created by the multiple signal echoes of the main signal.
- the television receiver has an internal antenna that is not readily accessible, one must manually rotate or adjust the entire television receiver in order to make the desired adjustment.
- a typical digital television signal is an ATSC 8-VSB signal.
- ATSC refer to the Advanced Television Standards Committee.
- 8-VSB refer to a television signal modulation format in which the television signal has eight vestigial sidebands.
- a typical television signal carrier frequency is in the frequency range from 470 MHz to 800 MHz.
- the present invention provides an apparatus and method for electronically modifying a television signal that is impaired by the presence of signal echoes of the main signal in order to minimize the signal echoes (i.e., null the interferers).
- Such electronic modification of a signal is referred to as beamforming.
- the invention comprises a beamforming circuit and a decision feedback equalizer circuit.
- the beamforming circuit comprises (1) two circuit branches with each circuit branch having a radio frequency (RF) tuner capable of being coupled to an antenna, an intermediate frequency (IF) mixer, a ⁇ /2 phase shift circuit and two feedforward equalizer circuits and (2) a first adder circuit.
- the beamforming circuit modifies the input signals to electronically form a beam in the direction of the desired signal and to electronically form a null in the direction of the interfering signal.
- a first antenna receives a signal and sends the signal through a first radio frequency (RF) tuner, through a first intermediate frequency (IF) mixer, and through a first analog-to-digital converter to a first feedforward equalizer circuit.
- the signal that goes through the first feedforward equalizer circuit is an "in-phase" component of the signal.
- the signal is also passed through a first ⁇ /2 phase shifter and through a second feedforward equalizer circuit.
- the signal that goes through the second feedforward equalizer circuit is a "quadrature" component of the signal.
- the phase of the quadrature component of the signal has been shifted from the phase of the original signal by an amount equal to ⁇ /2 radians or ninety degrees (90°).
- a second antenna receives a signal and sends the signal through a second RF tuner, through a second IF mixer, and through a second analog-to-digital converter to a third feedforward equalizer circuit.
- the signal that goes through the third feedforward equalizer circuit is an "in-phase" component of the signal.
- the signal is also passed through a second ⁇ /2 phase shifter and through a fourth feedforward equalizer circuit.
- the signal that goes through the fourth feedforward equalizer circuit is a "quadrature" component of the signal.
- the phase of the quadrature component of the signal has been shifted from the phase of the original signal by an amount equal to ⁇ /2 radians or ninety degrees (90°).
- the output of the first feedforward equalizer circuit and the output of the second feedforward equalizer circuit and the output of the third feedforward equalizer circuit and the output of the fourth feedforward equalizer circuit are added together in a first adder circuit and are used as the input to the decision feedback equalizer circuit.
- the beamforming circuit comprises the first circuit branch from the first RF tuner to the first and second feedforward equalizer circuits together with the second circuit branch from the second RF tuner to the third and fourth feedforward equalizer circuits together with the first adder circuit.
- the decision feedback equalizer circuit comprises a second adder circuit, a decision device and a feedback equalizer circuit.
- the second adder circuit is the first element of the decision feedback equalizer circuit.
- the second adder circuit receives a signal from the first adder circuit of the beamforming circuit and combines that signal with a signal from the feedback equalizer circuit to create an input signal to the decision device.
- the feedback equalizer circuit is connected to the output of the decision device to sample the output signal that leaves the decision device.
- the feedback equalizer circuit feeds a modified form of that output signal back to the second adder circuit for use in creating an input signal to the decision device as described above.
- the decision device calculates the error in the received signal that is due to an interfering signal arising from an echo of the main signal.
- the decision device uses an adaptation algorithm to calculate corrections to the signal.
- the decision device applies those corrections to the signal to electronically form a beam in the direction of the desired signal and to electronically form a null in the direction of the interfering signal.
- the result is a significant improvement in the quality of signal reception.
- the decision device also has control lines that are coupled to the first feedforward equalizer circuit and to the second feedforward equalizer circuit and to the third feedforward equalizer circuit and to the fourth feedforward equalizer circuit and to the feedback equalizer circuit.
- the decision device can send control signals over the control lines to change any or all of the coefficients in these five equalizer circuits to modify the operating characteristics of the equalizer circuits.
- the terms "include” and “comprise” and derivatives thereof mean inclusion without limitation;
- the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like;
- the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware, or software, or some combination of at least two of the same.
- FIGURE 1 is a block diagram of an adaptive digital beamforming receiver of the present invention
- FIGURE 2 is a block diagram of a high definition television signal receiver in which the present invention may be embodied.
- FIGURE 3 is a block diagram of an embodiment of the present invention in a signal receiver of a video device;
- FIGURE 4 is a flow diagram illustrating the operation of an exemplary adaptive beamforming receiver in accordance with one embodiment of the present invention.
- FIGURES 1 through 4 discussed below, and the various embodiments used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any suitably arranged signal receiver.
- FIGURE 1 illustrates an adaptive digital beamforming receiver 100, according to a preferred embodiment of the invention.
- the invention comprises beamforming circuit 200 and decision feedback equalizer circuit 300.
- Beamforming circuit 200 comprises two branches.
- the first branch of beamforming circuit 200 comprises radio frequency (RF) tuner 222, which is capable of being coupled to antenna 220.
- RF tuner 222 is coupled to intermediate frequency (IF) mixer 224.
- IF mixer 224 down-convert the RF signal received from antenna 220 to an analog baseband signal.
- IF mixer 224 is coupled to analog-to-digital converter 226, which converts the analog baseband signal to a digital baseband signal.
- Analog-to-digital converter 226 is coupled to first feedforward equalizer circuit 228 and first B/2 phase shift circuit 230.
- First B/2 phase shift circuit 230 is connected to second feedforward equalizer circuit 232.
- First B/2 phase shift circuit 230 shifts by 90 degrees the digital baseband signal at the input of second feedforward equalizer 232 with respect to the baseband signal at the input of first feedforward equalizer 228.
- first feedforward equalizer circuit 228 modifies the input signal to form a beam in the direction of the desired signal and to form a null in the direction of the interfering signal.
- second feedforward equalizer circuit 232 modifies the B/2 phase shifted input signal to form a beam in the direction of the desired signal and to form a null in the direction of the interfering signal.
- the second branch of beamforming circuit 200 comprises radio frequency (RF) tuner 242, which is capable of being coupled to antenna 240.
- RF tuner 242 is coupled to intermediate frequency (IF) mixer 244. Together, RF tuner 242 and IF mixer 244 down- convert the RF signal received from antenna 240 to an analog baseband signal.
- IF mixer 244 is coupled to analog-to-digital converter 246, which converts the analog baseband signal to a digital baseband signal.
- Analog-to-digital converter 246 is coupled to third feedforward equalizer circuit 248 and second B/2 phase shift circuit 252.
- Second B/2 phase shift circuit 252 is connected to fourth feedforward equalizer circuit 254.
- Second B/2 phase shift circuit 230 shifts by 90 degrees the digital baseband signal at the input of fourth feedforward equalizer 254 with respect to the baseband signal at the input of third feedforward equalizer 252.
- third feedforward equalizer circuit 248 modifies the input signal to form a beam in the direction of the desired signal and to form a null in the direction of the interfering signal.
- fourth feedforward equalizer circuit 254 modifies the B/2 phase shifted input signal to form a beam in the direction of the desired signal and to form a null in the direction of the interfering signal.
- first adder circuit 250 adds together the output signals from feedforward equalizer circuits 228, 232, 248 and 254.
- the signal that results from the addition of the signals by first adder circuit 250 is an improved signal because it represents a combination of four separate signals, each of which has been modified to form a beam in the direction of the desired signal and modified to form a null in the direction of the interfering signal. Signal information that may have been missing from one of the signals (due to interference) may have been present in one of the other signals.
- Antennas 220 and 240 may be vertical, single dipole, omni-directional antennas. Antennas 220 and 240 are spaced apart by a distance in the range from one- twentieth (1/20) of a wavelength of the received signal up to one (1) wavelength of the received signal. For example, in the case of a carrier frequency of 470 MHz, the maximum separation of antennas 220 and 240, would be approximately 0.63 meter or approximately 24.0 inches. Antennas 220 and 240 can be used as components of an internal antenna of a television receiver that uses the present invention.
- First feedforward equalizer circuit 228 receives from first analog-to-digital converter 226 a digital form of the signal received by antenna 220.
- First feedforward equalizer circuit 228 comprises circuitry (not shown) for operating a signal processing algorithm that is designed to compensate for the distortions in the amplitude and in the phase that a signal may acquire when that signal is transmitted through a dispersive channel. In this instance, the dispersive channel is the atmosphere.
- a number of different types of prior art feedforward equalizer circuits are available that may be used as the first feedforward equalizer circuit 228 of the present invention.
- One of the simplest types of equalizer circuits is the Linear Transversal Equalizer.
- the Linear Transversal Equalizer samples values of the input signal in a tapped delay line having N tap points and multiplies those sampled values by N numerical coefficients and then sums the resultant values to form a representation of the signal.
- the numerical coefficients are numbers that represent weight factors. The number of numerical coefficients can range from one coefficient up to, for example, one hundred coefficients or more.
- the resultant signal is represented mathematically as follows:
- third feedforward equalizer circuit 248 receives from second analog- to-digital converter 246 a digital form of the signal received by antenna 240.
- Third feedforward equalizer circuit 248 may be identical in structure and function to the first feedforward equalizer circuit 228.
- the output signal of the third feedforward equalizer circuit 248 is represented mathematically as follows:
- Second feedforward equalizer circuit 232 receives from first B/2 phase shift circuit 230 a phase shifted digital form of the signal received by antenna 220.
- Second feedforward equalizer circuit 232 is identical in structure and function to the first feedforward equalizer circuit 228. The only difference is that the signal has been phase shifted by B/2 radians. This shift is represented by the factor e* (B/2) .
- the output signal of the second feedforward equalizer circuit 232 is represented mathematically as follows:
- y n is the output
- x l n is the n ⁇ sample of the input signal from the first antenna 220
- a'j are the coefficients of second feedforward equalizer 232
- N is the number of coefficients in the second feedforward equalizer 232.
- the output signal of the fourth feedforward equalizer circuit 254 is represented mathematically as follows:
- ⁇ 0 where y n is the output, x >n is the n ⁇ sample of the input signal from the second antenna 240, b' j are the coefficients of fourth feedforward equalizer 254, and N is the number of coefficients in the fourth feedforward equalizer 254.
- Linear Transversal Equalizer in this description does not limit the invention to this particular type of equalizer. Other types of equalizers may be utilized to practice the invention.
- the decision feedback equalizer circuit 300 of the invention comprises a second adder circuit 320, a decision device 330, and a feedback equalizer circuit 340.
- the second adder circuit 320 of decision feedback equalizer circuit 300 is coupled to the first adder circuit 250 of beamforming circuit 200.
- the second adder circuit 320 receives from the first adder circuit 250 a signal that is the sum of the output signal from first feedforward equalizer circuit 228 and the output signal from second feedforward equalizer circuit 232 and the output signal from third feedforward equalizer circuit 248 and the output signal from fourth feedforward equalizer circuit 254.
- second adder circuit 320 also receives an input signal from feedback equalizer circuit 340.
- Second adder circuit 320 is coupled to a decision device 330. Decision device
- DSP digital signal processor
- Decision device 330 performs two operations. The first operation is to make a decision as to which valid symbol the input symbol is closest to (in this case, the eight levels of the 8-VSB signal). This could be called a splicer. It is this valid symbol (i.e., the decision output) that is passed to the feedback equalizer circuit 340. The second operation of decision device 330 is based on the difference of the decision device input and the decision device output (i.e., the symbol error).
- the symbol error is used in a decision directed adaptation algorithm (e.g., Least Mean Square Algorithm) or in a blind adaptation algorithm (e.g., Constant Modulus Algorithm) to update the equalizer coefficients so that the Mean Square Error (MSE) at the decision device input is reduced.
- Decision device 330 may use any one of a number of equalizer adaptation algorithms well known in the prior art.
- the equalizer adaptation algorithm used is the Least Mean Squares (LMS) method. It is referred to as the LMS algorithm.
- Another equalizer adaptation algorithm available for use utilizes the Recursive Least Squares (RLS) method. It is referred to as the RLS algorithm.
- RLS Recursive Least Squares
- Other similar algorithms are also available for use. The description of the preferred embodiment of the invention is not intended to limit the type of algorithm that may be used in accordance with the concept of the invention.
- the adaptation algorithm calculates the amount of error in the amplitude and phase of the signal.
- the adaptation algorithm then calculates the amount of correction needed to correct the errors.
- the decision device 330 then changes the values of the coefficients in first feedforward equalizer 228, second feedforward equalizer 232, third feedforward equalizer 248, fourth feedforward equalizer 254, and feedback equalizer 340. In this manner, decision device 330 modifies the signal to create an improved signal by electronically forming a beam in the direction of the desired signal and by electronically forming a null in the direction of the interfering signal.
- Feedback equalizer circuit 340 is coupled to the output of decision device 330 for sampling the output signal of decision device 330.
- Feedback equalizer circuit 340 also has an output coupled to an input of second adder circuit 320. This allows second adder circuit 320 to access the output signal of feedback equalizer circuit 340.
- Second adder circuit 320 subtracts the output signal of feedback equalizer circuit 340 from the signal that is the sum of the output signal from first feedforward equalizer circuit 228 and the output signal from second feedforward equalizer circuit 248 and the output signal from third feedforward equalizer circuit 248 and the output signal from fourth feedforward equalizer circuit 254.
- Feedback equalizer circuit 340 may also have the same form and structure of the first feedforward equalizer circuit 228 and the second feedforward equalizer circuit 248 and the third feedforward equalizer circuit 248 and the fourth feedforward equalizer circuit 254.
- the output signal of feedback equalizer circuit 340 is represented mathematically as follows: where y n is the output, y n . k is the input signal from the decision device 330, C are the coefficients of feedback equalizer circuit 340, and M is the number of coefficients in feedback equalizer circuit 340. Therefore, the input signal to the decision device 330 is given by the mathematical expression:
- y n ( c k y n _ k where y n is the estimated output, x ljn is the n ⁇ sample of the input signal from first antenna 220, x 2(self is the n ⁇ sample of the input signal from second antenna 240, and y n-k is the input signal from the decision device 330.
- the values aj are the coefficients of the first feedforward equalizer circuit 228, the values a'; are the coefficients of the second feedforward equalizer circuit 248, the values b j are the coefficients of the third feedforward equalizer circuit 248, the values b' j are the coefficients of the fourth feedforward equalizer circuit 254, and the values c ⁇ _ are the coefficients of the feedback equalizer circuit 340.
- the value N is the number of coefficients in feedforward equalizer circuit 228, feedforward equalizer circuit 232, feedforward equalizer circuit 248, and feedforward equalizer circuit 254.
- the value M is the number of coefficients in the feedback equalizer circuit 340. This expression represents the input to the decision device 330.
- Decision device 330 utilizes the above described input value for yford to sequentially set up and solve a set of linear equations to determine corrected values for the coefficients of each of the five equalizer circuits, that is, for the first feedforward equalizer circuit 228, and for the second feedforward equalizer circuit 232, and for the third feedforward equalizer circuit 248, and for the fourth feedforward equalizer circuit 254, for the feedback equalizer circuit 340.
- the coefficients (also referred to as tap weights) of an equalizer can be adjusted to minimize the Mean Square Error (MSE), ⁇ k , according to:
- a set of linear equations can be set up based on the orthogonality principle in mean-square estimation.
- the equalizer coefficients, d J? are chosen such that the Mean Square
- MSE Error
- LMS Least Mean Square
- Mean Square Error can be found and the opposite of this taken to update the tap values so that the MSE moves closer to the minimum.
- the value ekX*(kT-nT) is an estimate of the gradient vector obtained from the data.
- the LMS algorithm does not require knowledge of the signal's statistics or of the noise.
- the new equalizer coefficient is deduced from the previous value of the coefficient minus an error function. The greater ⁇ is, the faster the convergence, and the smaller ⁇ is, the slower the convergence.
- the LMS algorithm is easy to implement but slow to converge.
- decision device 330 After decision device 330 has calculated the new equalizer coefficients for the equalizer circuits, decision device 330 sends a new equalizer coefficient to first feedforward equalizer circuit 228 via control line 331. Decision device 330 also sends a new equalizer coefficient to second feedforward equalizer circuit 232 via control line 333, sends a new equalizer coefficient to third feedforward equalizer circuit 248 via control line 335, sends a new equalizer coefficient to fourth feedforward equalizer circuit 254 via control line 337, and sends a new equalizer coefficient to feedback equalizer 340 via control line 339.
- the decision device 330 creates an improved signal for signal receiver 400.
- a video device will be briefly described.
- the video device that will be described is a high resolution television signal receiver. It is to be borne in mind that the invention is not limited to use in a television signal receiver but may be used in any type of video device, including, without limitation, personal computer monitors, laptop computer monitors, handheld computer monitors, handheld video devices, and any type of device having the ability to display a video signal.
- FIGURE 2 is a block diagram of a high definition television signal receiver, in which the present invention may be embodied.
- the television signal is received by antenna 520 and sent to a RF tuner 522 and then to an IF mixer 524.
- the signal is then sent to a demodulator and channel decoder circuit 526.
- the signal is then sent to a transport demultiplexer and decryption circuit 530 where the audio, video and data portions of the signal are separated from each other.
- the video portion of the signal is sent to a video decoder 540.
- the audio portion of the signal is sent to an audio decoder 542.
- the data portion of the signal is sent to a data decoder 544.
- the video portion of the signal is sent to a video display circuit 550 and the audio portion of the signal is sent to an audio speaker unit 552.
- FIGURE 3 is a block diagram of an embodiment of the present invention in a video device 600.
- the video device 600 is a television signal receiver having a first antenna 520 and a second antenna 521.
- the RF tuner 522 and the IF mixer 524 of the television signal receiver 500 have been replaced with the beamforming circuit 200 and with the decision feedback equalizer circuit 300 of the present invention.
- FIGURE 3 is an exemplary adaptive digital beamforming receiver of the present invention.
- the decision feedback equalizer circuit 300 sends the improved signal of the present invention to an MPEG-2 decoder 620.
- the MPEG-2 decoder 620 is of a type well known in the prior art.
- the video portion of the signal is sent to a video display unit 630.
- the audio portion of the signal is sent to an audio speaker 640.
- FIGURE 4 is a flow diagram illustrating the operation of an exemplary adaptive digital beamforming receiver in accordance with one embodiment of the present invention.
- Step 700 comprises the step of demodulating a first analog signal from a first antenna.
- Step 702 comprises the step of converting the first analog signal to a digital signal.
- Step 704 comprises the step of modifying the first signal in a first feedforward equalizer to correct distortions in the first signal.
- step 706 comprises the step of demodulating a second analog signal from a second antenna.
- step 708 comprises the step of converting the second analog signal to a digital signal.
- step 710 comprises the step of modifying the second signal in a second feedforward equalizer circuit to correct distortions in the second signal.
- Step 712 comprises the step of adding the modified first signal and the modified second signal.
- Step 714 comprises the step of adding to the sum of the modified first signal and the modified second signal a feedback signal from a feedback equalizer circuit to create an improved signal.
- Step 716 comprises the step of modifying the improved signal in a decision device having an adaptive algorithm by adjusting the coefficients of the first feedforward equalizer circuit, and by adjusting the coefficients of the second feedforward equalizer circuit, and by adjusting the coefficients of the feedback equalizer circuit.
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- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Multimedia (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP00972684A EP1142160A1 (en) | 1999-10-21 | 2000-10-05 | AN ADAPTIVE DIGITAL BEAMFORMING RECEIVER WITH $g(p)/2 PHASE SHIFT TO IMPROVE SIGNAL RECEPTION |
KR1020017007896A KR20010086140A (en) | 1999-10-21 | 2000-10-05 | An adaptive digital beamforming receiver with π/2 phase shift to improve signal reception |
JP2001531225A JP2003512762A (en) | 1999-10-21 | 2000-10-05 | Adaptive digital beamforming receiver with π / 2 phase shift to improve signal reception quality |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/422,734 US6115419A (en) | 1999-10-21 | 1999-10-21 | Adaptive digital beamforming receiver with π/2 phase shift to improve signal reception |
US09/422,734 | 1999-10-21 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2001029987A1 true WO2001029987A1 (en) | 2001-04-26 |
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Family Applications (1)
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PCT/EP2000/009761 WO2001029987A1 (en) | 1999-10-21 | 2000-10-05 | AN ADAPTIVE DIGITAL BEAMFORMING RECEIVER WITH π/2 PHASE SHIFT TO IMPROVE SIGNAL RECEPTION |
Country Status (5)
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US (1) | US6115419A (en) |
EP (1) | EP1142160A1 (en) |
JP (1) | JP2003512762A (en) |
KR (1) | KR20010086140A (en) |
WO (1) | WO2001029987A1 (en) |
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US7292661B1 (en) * | 2000-03-20 | 2007-11-06 | Massachusetts Institute Of Technology | Block-iterative equalizers for digital communication system |
US7010029B1 (en) * | 2000-04-13 | 2006-03-07 | At&T Corp. | Equalization of transmit diversity space-time coded signals |
IT1317249B1 (en) * | 2000-04-14 | 2003-05-27 | Cit Alcatel | METHOD AND APPARATUS FOR THE AUTOMATIC COMPENSATION OF THE DELAY FOR RADIO TRANSMISSIONS IN DIFFERENT SPACE. |
US6650702B1 (en) * | 2000-05-15 | 2003-11-18 | Lockheed Martin Corp. | Blind initialization of decision feedback equalizer using an antenna array |
US6950477B2 (en) * | 2001-01-16 | 2005-09-27 | Joseph Meehan | Blind dual error antenna diversity (DEAD) algorithm for beamforming antenna systems |
US20020150185A1 (en) * | 2001-03-29 | 2002-10-17 | Joseph Meehan | Diversity combiner for reception of digital television signals |
US7034893B2 (en) * | 2001-03-30 | 2006-04-25 | Broadcom Corporation | Method and apparatus for reception of terrestrial digital television signals |
US6691181B2 (en) * | 2001-10-09 | 2004-02-10 | Phillip M. Adams | Programmatic time-gap defect detection apparatus and method |
ITMI20012631A1 (en) * | 2001-12-13 | 2003-06-13 | Marconi Comm Spa | MEDIUM SQUARE ERROR-BASED METHOD FOR ADAPTIVE ADJUSTMENT OF PMD COMPENSATORS IN OPTICAL FIBER AND COMMUNICATION SYSTEMS |
US6980614B2 (en) * | 2002-01-14 | 2005-12-27 | Raytheon Company | System and method for subband beamforming using adaptive weight normalization |
US20030228860A1 (en) * | 2002-06-06 | 2003-12-11 | Chewnpu Jou | Integrated radio-frequency receiver |
KR100911142B1 (en) * | 2002-12-02 | 2009-08-06 | 삼성전자주식회사 | Equalizer for high density optical disc reproducing apparatus and equalizing method therefor |
US7103383B2 (en) * | 2002-12-31 | 2006-09-05 | Wirless Highways, Inc. | Apparatus, system, method and computer program product for digital beamforming in the intermediate frequency domain |
KR100510678B1 (en) * | 2003-03-19 | 2005-08-31 | 엘지전자 주식회사 | Smart antenna control system for digital TV |
US20050129148A1 (en) * | 2003-12-11 | 2005-06-16 | Wideband Semiconductors, Inc. | Control algorithm in QAM modems |
US7526022B2 (en) * | 2004-05-19 | 2009-04-28 | Harris Corporation | Low complexity equalizer |
US7295618B2 (en) * | 2004-06-16 | 2007-11-13 | International Business Machines Corporation | Automatic adaptive equalization method and system for high-speed serial transmission link |
JP4405375B2 (en) * | 2004-12-07 | 2010-01-27 | 三菱電機株式会社 | Digital broadcast receiver |
KR100836969B1 (en) * | 2005-08-05 | 2008-06-10 | 세이코 엡슨 가부시키가이샤 | Receiving device |
KR100782820B1 (en) * | 2005-09-30 | 2007-12-06 | 삼성전자주식회사 | Printing apparatus having broadcast receiver and operating method thereof |
US20080205563A1 (en) * | 2007-02-09 | 2008-08-28 | Simpson Richard D | Digital Filter |
US8902365B2 (en) * | 2007-03-14 | 2014-12-02 | Lance Greggain | Interference avoidance in a television receiver |
US8330873B2 (en) * | 2007-03-14 | 2012-12-11 | Larry Silver | Signal demodulator with overmodulation protection |
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US9036689B2 (en) * | 2012-03-29 | 2015-05-19 | Terasquare Co., Ltd. | Variable-precision distributed arithmetic multi-input multi-output equalizer for power-and-area-efficient optical dual-polarization quadrature phase-shift-keying system |
US10998627B2 (en) * | 2017-10-23 | 2021-05-04 | Nec Corporation | Phase adjustment circuit and array antenna device |
US10425256B2 (en) * | 2018-02-06 | 2019-09-24 | Huawei Technologies Canada Co., Ltd. | Methods and systems for interference mitigation in a dual-polarized communication system |
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- 2000-10-05 WO PCT/EP2000/009761 patent/WO2001029987A1/en active Application Filing
- 2000-10-05 KR KR1020017007896A patent/KR20010086140A/en active IP Right Grant
- 2000-10-05 EP EP00972684A patent/EP1142160A1/en not_active Withdrawn
- 2000-10-05 JP JP2001531225A patent/JP2003512762A/en active Pending
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US5929811A (en) * | 1995-03-28 | 1999-07-27 | Rilling; Kenneth F. | Adaptive array with automatic loop gain control |
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Also Published As
Publication number | Publication date |
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KR20010086140A (en) | 2001-09-07 |
JP2003512762A (en) | 2003-04-02 |
US6115419A (en) | 2000-09-05 |
EP1142160A1 (en) | 2001-10-10 |
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